I've been dating this guy for a month, and we just recently started sleeping together. The thing is, he never lets me sleep over and won't stay at my place either. After sex, he'll cuddle for half an hour, then he'll make up an excuse about having to go or he'll ask if he can drive me home. He seems to like me, so why wouldn't he want me to spend the night?

Most likely, it's a commitment thing. A little sleepover might seem harmless and sweet to you, but to a guy, it's one step closer to coupledom. This sounds crazy, I know. You're already having sex, so how could sleeping together be an earth-shattering event? Here's how: Just the act of waking up next to you and possibly having breakfast together signifies to him that you're an item. Morning time also means morning breath, morning wood, bedhead, groggy pillow talk, and other intimacies. Your guy isn't ready for that kind of closeness yet. It may not be the most mature approach, but taking off is his way of flashing the let's-take-it-slow yellow light. There may still be relationship potential; it's just too soon to tell. Give him a little more time to sort things out in his head. Generally, it takes guys longer to be comfortable with the cuddly stuff. If after month two, however, he still wants to cut the night short, then I think you deserve an explanation. Ask him, in a nonaccusatory way, why he won't spend the night. After he gives his reason  which will probably be some BS excuse like "I have to get up early for work"  tell him how you feel. Say "If we're going to continue having sex, then it's important to me that we spend the night together." Hopefully, he cares enough about keeping you in his life that he'll get past his sleepover aversion.